Refactor keybinding handling and update widgets

- Remove the old `keybindings.rs` and stop re‑exporting its symbols.
- Add view‑specific handling: `App::handle_key_event` now delegates to
  `main_menu_keybindings` when the view is `MainMenu`.
- Update imports in `app.rs`, `widget.rs`, and widget modules to use the
  new `app::keybindings` path.
- Enhance `keybindings_widget` to display ↑, ↓ and “Space” for special
  keys.
- Change main menu layout percentages from 90/10 to 87/13.
- Reorder the `clap` import in `cli.rs` for consistency.

src/app/keybindings/keybindings.rs

@@ -0,0 +1,73 @@
+use crate::app::View;
+use ratatui::crossterm::event::{KeyCode, KeyEvent, KeyEventKind, KeyModifiers};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Action {
+    Quit,
+    ScrollUp,
+    ScrollDown,
+    Select,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct KeyBinding {
+    pub action: Action,
+    pub code: KeyCode,
+    pub kind: KeyEventKind,
+    pub modifiers: KeyModifiers,
+    pub description: &'static str,
+}
+
+pub static KEYBINDINGS: &[KeyBinding] = &[
+    KeyBinding {
+        action: Action::Quit,
+        code: KeyCode::Char('q'),
+        kind: KeyEventKind::Press,
+        modifiers: KeyModifiers::NONE,
+        description: "Quit",
+    },
+    KeyBinding {
+        action: Action::ScrollUp,
+        code: KeyCode::Up,
+        kind: KeyEventKind::Press,
+        modifiers: KeyModifiers::NONE,
+        description: "Up",
+    },
+    KeyBinding {
+        action: Action::ScrollDown,
+        code: KeyCode::Down,
+        kind: KeyEventKind::Press,
+        modifiers: KeyModifiers::NONE,
+        description: "Down",
+    },
+    KeyBinding {
+        action: Action::Select,
+        code: KeyCode::Char(' '),
+        kind: KeyEventKind::Press,
+        modifiers: KeyModifiers::NONE,
+        description: "Select",
+    },
+];
+
+pub fn binding_for(action: Action) -> Option<&'static KeyBinding> {
+    KEYBINDINGS.iter().find(|b| b.action == action)
+}
+
+pub fn event_to_action(event: &KeyEvent) -> Option<Action> {
+    KEYBINDINGS
+        .iter()
+        .find(|b| b.code == event.code && b.kind == event.kind && b.modifiers == event.modifiers)
+        .map(|b| b.action)
+}
+
+pub fn binding_for_view(view: View) -> Vec<&'static KeyBinding> {
+    match view {
+        View::MainMenu => vec![
+            binding_for(Action::ScrollUp).unwrap(),
+            binding_for(Action::ScrollDown).unwrap(),
+            binding_for(Action::Select).unwrap(),
+            binding_for(Action::Quit).unwrap(),
+        ],
+        _ => vec![],
+    }
+}